Structurally rigid and semirigid agents which will fit the catecholamine receptor sites of the CNS and PNS will be synthesized. A knowledge of that conformation which acts as an agonist or antagonist will allow a more systematic approach to the mechanism of action as well as to the design of drugs with greater specificity. These agents will be assayed in intact animals, isolated organs, and as substrates and inhibitors for those enzymes which are involved in the synthesis or degradation of catecholamines.